My wife and I are in our early 60's and have cruised 11 times on various cruise lines with all size ships. We had finished a 7 day cruise on the Royal Caribbean Allure just before we our 7 day Eastern caribbean cruise on the NCL Epic. Both ships are big! The Epic feels crowded and cramped all of the time from the top deck to the corridors while the Allure is big but does not feel like there are 5000 people on it. It's public areas are airy and open except possibly for the buffet. The Epic wave-designed rooms seemed like a good idea until you are in one. The rooms are so narrow you cannot pass one another easily. The Epic's design of the separate toilet and separate showers with only frosted glass walls and a curtain to divide them from the rest of the room is a very poor design idea. You have zero privacy. It prevents you from having other passengers over to visit while you finish getting ready. In contrast, the Allure has a conventional private bathroom design and the balcony room is wide enough to even have a small coffee table.
Wait times for Epic's elevators were almost always long with many giving up and choosing to take the stairs. The Epic simply does not seem to have enough elevators to handle the people and not nearly as many elevators as the Allure.
The Epic has a good portion of its sundeck taken up with the ultra plush HAVEN area with its own pool and restaurant. That leaves only about 3/4's of the deck for the other 3000 plus people and there are only two pools with signs saying a max of 75 in each pool (plus a very small pool in the adult area) while the Allure has 6 pools.
The Epic's public areas have lower ceilings and feel more claustrophobic than Allure's public areas and long multistory open promenade area. Having the casino located where it is means that patrons headed to the main complimentary restaurants must walk through all of the smokey confines of the casino area to get there.
The complimentary restaurants on the Epic are very nice, spacious and have consistently tasty food. The service however is less than great -we had to get up and fill our own water glasses several times at different restaurants during the cruise.They don't seem to have enough servers for the number of people. Possibly the mandatory tipping policy results in staff that don't feel they have to work quite as hard for tips. Unlike other cruises, we never saw our cabin steward during the entire week.
The Epic's entertainment is terrific (Blue Man Group and Legends from Vegas) but the theater venue is small for such a big ship. Be sure to get your reservations ahead of time. The cirque show was fun and worth the cost. We did not opt for the premium seating and had a nice booth but did have some view obstruction by the ceiling on one of the acts that were performed higher up.
St Thomas is a beautiful port. We took an excursion to Magen's Beach that was well worth it. Our next stop was St Maarten which is also a great place to visit - the water taxi takes you right to the middle of the town. Shopping is great. The beach is right there when you get off the water taxi. Rent an umbrella and chair and have a great afternoon. Nassau has shopping a very short walk from the pier. We went to the straw market which was fun to walk through.
We had a good time but the ship design really isn't great to be so newly built.
So in summary, the food and entertainment are very good, the ship and room designs are bad and the service was not so good. Given the choice of a big ship cruise I would choose either the RCCL Allure or the Oasis over the Epic next time.